TLE7189F

Data Sheet

22

Rev. 2.1, 2007-05-30

5.3

Shunt Signal Conditioning

The TLE7189F incorporates three fast and precise operational amplifiers for conditioning and amplification of the

shunt signals sensed in the three phases. Additionally, one reference bias buffer is integrated to provide an

adjustable bias reference for the three OpAmps. The voltage divider on the VRI pin should be less than 50 k

Ω, the

filtering capacitor less than 1.2 µF - if needed at all. The gain of the OpAmps is adjustable by external resistors

within a range of 3 to 20 or more, as long as the band width satisfies the need of the application.

In the circuit example below VO1 provides the reference voltage

V

normally half of the regulated voltage provided from an external voltage regulator for the ADC used to read the

current sense signal. The additional buffer allows bi-directional current sensing and permits the adaptation of the

reference bias to different µC I/O voltages. The reference buffer assures a stable reference voltage even in the

high frequency range.

The reference bias buffer is used for all of the OpAmps. The OpAmps of the TLE7189F demonstrate low offset

voltages and very little drift over temperature, thus allowing accurate phase current measurements.

Figure 4

Shunt Signal Conditioning Block Diagram

VRI

VRO

ISP1

ISN1

-

+

Shunt

Rfb

Rfb

Rs

Rs

VO1

Bias

Reference

I-DC Link

OpAmp1

3.3V

ISP2

ISN2

I-DC Link

OpAmp2

VO2

ISP3

ISN3

I-DC Link

OpAmp3

VO3

Rfb

Rfb

Rs

Rs

Rs

Rs

to ADCs

TLE7189

Adjustable

bias

reference

R

VRI

R

VRI

C

VRI

C

R

1k

1k

Dependent on

customer specific

requirements additional

filtering can be

necessary